A projector is a kind of display and has several advantages such as projecting an image of large size that is several times than a surface area of the projector having small size. Therefore, projectors have superiority in the display field.
In general, the projector is capable of producing images by using a light valve which produces an image beam for being projected onto a projection screen The light valve may be a digital micro-mirror device (DMD), a liquid-crystal-on-silicon panel (LCOS panel), and a transmissive liquid crystal panel.
Each pixel of the DMD is formed by one or more micro-reflective mirrors and each micro-reflective mirror may have three rotating locations, namely an on state, an off state, and a flat state. The light beam is reflected to the projection lens when the micro-reflective mirror is at the on state, the light beam is deviated from the projection lens when the micro-reflective mirror is at the off state, and the micro-reflective mirror does not deflect when it is at the flat state. In general, the micro-reflective mirror is tilted to a direction with an angle when the micro-reflective mirror rotates from the flat state to the on state. On the other hand, the micro-reflective mirror is tilted to the opposite direction with an angle when the micro-reflective mirror rotates from the flat state to the off state.
However, an area of a flat-state light beam reflected by the micro-reflective mirror and an area of a on-state light beam reflected by the micro-reflective minor may be partially overlapped such that some flat-state light beams transmit into a projection lens of an imaging assembly is projected to an outer projection screen, thereby resulting in a stray light, and thus a contrast of an image projected onto the outer projection screen may be decreased.
In order to solve the influence caused by the stray light, a shield is conventionally disposed in an inner of the projector to avoid the stray light transmitting into the projection lens, however, the shield may cover some of the on-state light beams forming the image beams such that a light extraction efficiency of the projector may be decreased.
The information disclosed in this BACKGROUND section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this BACKGROUND section does not mean that one or more problems to be solved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.